Novel Cues Explicitly Signaling Shock Omission Alter Fear Extinction Learning in a Sex and Context Dependent Manner: A Role for Dopamine in a Novelty-based Extinction Paradigm

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/t435gf77t

Abstract

Although associating stimuli with potential threats in the environment is vital for survival, it is equally important to learn when those same stimuli no longer pose any viable threat, a different type of associative learning called fear extinction. The memory formed in fear extinction is very vulnerable to disruption and this vulnerability poses problems for individuals with PTSD who seek to decrease fear to a particular set of stimuli. Prediction errors are vital to fear extinction learning and it is possible that by increasing the prediction error at the time of threat omission, the extinction memory may become less vulnerable to disruption. To test this, a novel light cue was presented during the shock omission in fear extinction (NBE treatment) and fear was assessed the following day. In addition, I recorded mPFC dopamine release during this task and assessed how cocaine experience alters NBE learning. Briefly, I found that NBE altered freezing in the inter-trial interval (ITI) in a sex and context dependent manner. Additionally, dopamine release in the mPFC increases at the novel cue presentation. Next, I found that cocaine experience prevents NBE learning and dopamine release in the mPFC to the novel cue. Finally, I saw that dopamine release at the novel cue in the prelimbic cortex is not necessary for NBE learning. Collectively, this suggests that novel cues can alter extinction learning and is dependent on general dopamine release but not prelimbic dopamine release.

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